In many mammals, including humans and some non-human primate species, the aging brain undergoes a[unreadable] number of large-scale changes that can be observed with imaging and cognitive approaches. These agerelated[unreadable] changes include structural atrophy, increased mineral deposition, decline in neurotransmitter[unreadable] production, periventricular ischemia, decline in glucose metabolism (and concomitant decline in certain higher[unreadable] cognitive functions, particularly in the domains of memory, cognitive speed, and executive function). The[unreadable] dramatic effect of diet restriction (DR) to increase lifespan in many species and its salutary effects on[unreadable] metabolic processes such as oxidative stress, suggest that this intervention may also be good for the brain. In[unreadable] this project, we propose to test the hypothesis that rhesus monkeys undergoing chronic DR will exhibit less[unreadable] pronounced age-related brain structural and functional changes than their ad libitum fed age-matched[unreadable] controls. We propose to test this hypothesis using high-resolution volumetric and microstructural Magnetic[unreadable] Resonance Imaging (MRI) techniques of the brain and cognitive tests. Our emphasis is on structures and[unreadable] cognitive functions that may change with age. We plan to accomplish the following specific aims: 1)[unreadable] determine if baseline differences exist between DR and control animals on tissue volume and integrity such[unreadable] as regional gray and white matter volume, T2 relaxation time (gray matter mineralization), magnetization[unreadable] transfer, and diffusion tensor imaging (white matter integrity). 2) determine whether cognitive differences exist[unreadable] between DR and control groups using computerized non-human primate behavioral paradigms that have[unreadable] previously been shown to be sensitive to age. 3) determine whether the rate of structural change has been[unreadable] slowed in the DR group. These aims will be accomplished utilizing the expertise and excellent resources of[unreadable] the Wisconsin Primate Research Center and the Keck Laboratory's 3-Tesla MRI. Analyses will examine the[unreadable] groups for baseline and longitudinal differences. The unique opportunity to study these animals with a[unreadable] comprehensive MRI imaging and cognitive battery should provide much needed information regarding global[unreadable] aging processes in the brain, and extend the evaluation of the effects of the DR intervention in domains of[unreadable] great significance to humans.